A gallium nitride based semiconductor device in which a semiconductor substrate on which the gallium nitride based device is formed is thinned to, in part, miniaturize the device and effect better heat transfer out of the device. Thinning of the semiconductor substrate is performed, for example, by backside grinding thereof, i.e., grinding away a surface of the substrate opposed to the side where the device is formed.
However, where a silicon substrate is used as the substrate on which a gallium nitride based device is formed, the resulting device has inherent stress due to the mismatch of the lattice constant of the silicon crystal and the lattice constant of the gallium nitride crystal. When performing backside grinding of the semiconductor substrate in such a situation, the silicon substrate may become excessively bent as a result of heat generated during the backside grinding. When the bending is excessive, the silicon substrate may break or fracture.